Multi-beveled point needle and syringe having a multi-beveled point needle

ABSTRACT

A syringe assembly including a needle cannula having a five-beveled point and a needle shield formed of a styrene block poly(ethylene/butylene) thermoplastic elastomer which significantly reduces needle penetration force and may reduce the cycle time for gas sterilization. The multi-beveled needle cannula point includes a primary bevel, a pair of tip bevels and a pair of middle bevels each intermediate the primary bevel and a respective tip bevel, wherein the angles of rotation of the primary bevel and the intermediate bevels are substantially equal resulting in reduced heights of intercepts between the bevels, therby reducing needle penetration force. The needle shield maintains the sharpness of the needle cannula during application, sterilization and removal of the shield and it is believed that the needle shield will also reduce the cycle time of gas sterilization as compared to rubber needle shields and vulcanizate thermoplastic elastomers.

RELATED APPLICATIONS

This application is a continuation-in-part application of Ser. No.09/809,469, of Mar. 15, 2001, now U.S. Pat. No. 6,629,963 whichapplication is a continuation in part application of Ser. No.09/454,993, of Dec. 6, 1999, now abandoned which application was acontinuation of Ser. No. 09/040,067, filed Mar. 17, 1998, now U.S. Pat.No. 6,009,933, which application was a divisional application of Ser.No. 08/670,255, filed Jun. 20, 1996, now U.S. Pat. No. 5,752,942.

FIELD OF THE INVENTION

The present invention relates to hypodermic syringes, particularlysterilized prefilled or prefillable syringes, having a multi-beveledpoint and a needle shield or sheath providing reduced needle penetrationforce.

BACKGROUND OF THE INVENTION

A hypodermic syringe typically includes a generally tubular barrelportion, which may be formed of glass or plastic, a plunger having astopper typically formed of an elastomeric material, such as rubber orsynthetic rubber, and a needle cannula typically formed from anelongated tube having a fluid-conducting lumen. Such syringes may beprefilled with a medicament, drug or vaccine which require a shield orsheath enclosing the sharp end of the needle cannula typically formed ofrubber or synthetic rubber. A needle shield includes an open end, aclosed end, and a needle passage through the open end which receives thesharp end of the syringe needle cannula. As will be understood,hypodermic syringes must be sterilized prior to use by the healthcareworker or patient and such syringes are typically sterilized by themanufacturer and generally sealed in a plastic container ready for use.

A preferred method of sterilizing hypodermic syringes, particularlyprefillable or prefilled syringes, is to “immerse” the syringe assemblyin a sterilizing gas, such as ethylene oxide. Although there are severalindustry recognized methods of gas sterilization, such methods dependupon permeation of the sterilization gas into the passage of the needleshield to sterilize the syringe needle cannula. However, natural andsynthetic rubber and vulcanizate thermoplastic elastomers arecharacterized as having a low gas permeability. Further, ethylene oxidegas, which is commonly used for gas sterilization. Alternatively, steamsterilization may also be used, but is generally limited to subsequentor “terminal” sterilization. As used herein, “sterilization gas” may beany gas used for sterilization, including ethylene oxide and steam.Therefore, the cycle time required for gas sterilization is relativelylong. That is, the syringe is first immersed in the sterilization gasfor a time sufficient for the gas to sterilize the syringe, includingthe needle cannula. Following sterilization, the sterilized syringes are“quarantined” for a time sufficient for the sterilization gas to escape,including any residual gas trapped in the needle shield. Thus, thesterilization cycle time is dependent in part upon how easily the gaspenetrates through the needle shield during sterilization and removal ofthe gas from the syringe assembly. Tests are conducted to confirm thatthe sterilized syringe assemblies contain only minute traces of residualethylene oxide or water in steam sterilization prior to release fordistribution or sale.

A particular concern with the design of syringes is reduction of theneedle cannula penetration force and patient comfort. The distal end orpoint of the needle cannula is typically provided with a tip geometryfor piercing a patient's epidermis, flesh or tissue to deliver a fluidmedicament, drug or vaccine stored or held in the syringe barrel. Ahealthcare worker or patient may also employ the syringe needle cannulato pierce an elastomeric septum or stopper of a vessel, such as a vial,to reconstitute dry or powdered medicament, drug or vaccine or toaspirate a liquid medicament, drug or vaccine contained in the vial.

Various considerations must be made when designing a syringe. Forexample, it is obviously desirable to minimize the needle cannulapenetration force necessary for urging the needle cannula point or tipthrough the epidermis and flesh of the patient. It is generally believedthat by reducing the needle cannula penetration force, the patient willperceive less pain. Another consideration in designing needle cannulapoint geometry is to prevent or minimize “coring”. Coring, as thoseskilled in this art understand, results when a portion of the materialthrough which the needle cannula has penetrated becomes lodged in thelumen adjacent the needle cannula tip.

Various attempts have been made to reduce the required penetration forceof syringe needle cannulas and reduce coring as discussed more fully inthe above-referenced co-pending application. These efforts have beenprimarily directed to improving the design of the needle cannula tip byproviding facets or bevels, for example, to reduce the requiredpenetration force. Other attempts have been made to minimize therequired penetration force by minimizing coring. However, these effortshave not been as successful as desired. Further, various efforts havebeen made to improve syringe needle cannula shields or sheaths,particularly for prefilled hypodermic syringes. Such improvementsgenerally relate to protecting the needle cannula and preventinginadvertent coring of the needle shield by the needle cannula asdisclosed, for example, in U.S. Pat. No. 4,964,866 assigned to theassignee of the present application, the disclosure of which isincorporated herein by reference. Further efforts have been made in thedesign of needle shields or syringes to reduce the gas sterilizationcycle time by providing non-linear channels in the needle cannula shieldwhich permit entry and egress of the sterilization gas while preventingentry of microorganisms.

However, no one has recognized the inter-relation between the selectionof the material from which the needle shield is formed and the requiredpenetration force of the needle cannula. The present invention relatesto an improved five-beveled point geometry for a hypodermic needle and aneedle shield which reduces the penetration force of the needle cannula.It is also believed that the improved needle shield will reduce gassterilization cycle time.

SUMMARY OF THE INVENTION

The syringe assembly of this invention utilizes an improved five-bevelneedle configuration which reduces penetration force and a needlecannula shield or sheath formed of a styrene block thermoplasticelastomer which maintains the sharpness of the needle cannula duringapplication, sterilization and removal of the shield, and may reduce thecycle time of gas sterilization. As described above, the improvedfive-beveled needle cannula configuration and needle shield may beutilized with any conventional injection device, including aconventional prefilled hypodermic syringe, and the improved needleshield or sheath of this invention has further advantages when thesyringe assembly is gas sterilized. A conventional syringe assemblyincludes a generally tubular barrel, typically made of glass, but whichmay also be formed from various polymers, a needle cannula fixed to thetip portion of the barrel having a lumen therethrough in fluidcommunication with the interior of the barrel portion and syringes.Prefillable and prefilled syringes include a needle shield having anopen end and a needle passage through the open end which receives thesharp distal end of the needle cannula to protect the needle cannula andprevent loss of fluid in the syringe barrel. The needle cannula istypically formed of stainless steel, such as AISI 304, and the needlecannula is generally coated with a lubricant, such as a silicone oil.U.S., Pat. No. 5,911,711 assigned to the assignee of this applicationdiscloses preferred needle lubricants. The needle shield or sheath istypically formed of a natural or synthetic rubber generally including asignificant amount of a filler to improve the mechanical properties andreduce cost. More recently, with the advent of thermoplastic elastomersreplacing rubber and synthetic rubber polymers in various applications,the prior art has suggested the use of thermoplastic elastomers forsyringe tip shields and tip caps. However, as set forth below, mostthermoplastic elastomers provide little if any advantage over natural orsynthetic rubber and vulcanizate thermoplastic elastomers suffer otherdisadvantages, including shrinkage during molding, lack of dimensionalstability and coring. There is, therefore, a need for an improved needlecannula point configuration which reduces penetration force and a needleshield which protects and maintains the sharpness of the needle cannulapoint.

It is believed by the inventors that a primary reason that a patientexperiences pain when a needle cannula penetrates the skin or flesh ofthe patient, the needle point catches on the. skin or flesh as theneedle penetrates. One cause of a needle point catching on the skin orflesh is believed to be due to the height of the “intersect” establishedat the transition between differing bevels forming the needle point. Itis believed that if this transition between differing bevels forming theneedle point is less pronounced, the height of the intersects would bereduced. The effect of reducing the heights of the transitions would beto approximate, from a series of bevels forming the cannula needlepoint, a more continuous, unitary bevel face. The resulting continuingbevel point would thus require less penetration force in entering apatient's skin and flesh. By reducing penetration force, it is believedthat the patient will also experience less pain.

Accordingly, one aspect of this invention relates to a multi-beveledneedle point, reducing the heights of the intersects created betweenmerging bevels that results in a more continuous bevel face. Asdescribed above, a needle cannula has a central lumen defining an axisthrough the needle cannula. The multi-beveled cannula needle pointdefines an opening to the lumen for the passage of fluids between amedical delivery device, such as a syringe, and a patient or vessel. Themulti-beveled point preferably includes a primary bevel, a pair of tipbevels, and a pair of middle bevels Each of the middle bevels arecontiguous with the primary bevel, and meet a respective one of the tipbevels at an intersect. The primary bevel is formed or otherwiseprovided on the cannula by inclining the central axis of the needlecannula to a first planar angle respective of a reference plane.

The needle point, formed of five distinct bevels, displays reducedheight intersects, resulting in a more continuous bevel face about theopening. It is believed that by providing a series of five distinctbevels, the needle point is lengthened over the needle pointsconventionally in use, and owing to the reduced height intervals,results in, an effective outer diameter at the needle point less thanthe outer diameter of the needle points currently in use, all of whichcontribute to reduced needle penetration force.

The needle shield of this invention is formed of a styrene blockthermoplastic elastomer, most preferably a styreneblock(polyethylene/butylene) thermoplastic elastomer having a Shore Ahardness of between 30 and 90 or more preferably between 45 and 65. Theneedle shield includes an open end and a passage through the open endconfigured to receive the needle cannula and preferably encloses theentire needle cannula and a portion of the syringe tip to fully protectthe cannula and prevent entry of microorganisms following sterilization.In the most preferred embodiment, the internal passage includes anintegral annular rib, adjacent the open end, which assures retention ofthe needle shield on the syringe tip portion and the needle shield ispreferably enclosed by a rigid cover or shield.

As discussed in more detail hereinbelow, the needle shield of thisinvention has several unanticipated and unexpected advantages overneedle shields formed of natural or synthetic rubber or conventionalvulcanizate thermoplastic elastomers. First, extensive bench andclinical testing has established that a needle cannula shield formed ofa styrene block thermoplastic elastomer, particularly a styrene blockpoly(ethylene/butylene) thermoplastic elastomer maintains the sharpnessof the needle cannula, particularly the needle cannula point, duringapplication and removal of the needle shield as compared to naturalrubber or synthetic rubber needle shields and conventional vulcanizatethermoplastic elastomers. This improvement results in reducedpenetration force which is now believed to result from at least twofactors which were discovered during clinical trials and bench testing.First, the needle cannula of a hypodermic syringe is conventionallycoated with a medical grade lubricant, such as a silicone oil lubricant,to reduce penetration force. It is now believed that a conventionalneedle shield wipes away the lubricant on the needle cannula,particularly at the needle point which is important to reduction ofpenetration force. As set forth above, a conventional needle shieldincludes a passage configured to receive the needle cannula and mostpreferably includes a small bore which closely receives the needlepoint. Thus, the lubricant may be wiped away during the receipt andremoval of the needle shield on the needle cannula. This was confirmedby electron microscopic examination of the needle cannula followinginsertion of the needle cannula in the needle shield and removal of theneedle shield from the needle cannula. The lubricant may also beabsorbed by the needle shield, particularly natural and synthetic rubberneedle shields having a high filler content. Second, needle shieldsformed of natural or synthetic rubber having a high filler content areabrasive, which may result in microabrasion of the needle point reducingthe sharpness of the needle. Regardless of the cause, however, bench andclinical testing has established that use of a needle shield formed of astyrene block poly(ethylene/butylene) thermoplastic elastomer results inless penetration force and improved sharpness as perceived by healthcareworkers making the injections. This improvement was unexpected.

Another potential advantage of a needle shield formed of a styrene blockthermoplastic elastomer, particularly a styrene blockpoly(ethylene/butylene) thermoplastic elastomer, is reduced atsterilization cycle time. As set forth above, syringe assemblies areconventionally sterilized with ethylene oxide gas, which is toxic.During sterilization, the syringe assembly is flooded or “immersed” inthe ethylene oxide gas or other sterilization gas including steam by oneof several known methods. As will be understood, the sterilization gasmust “penetrate” the needle shield to sterilize the needle cannula.However, rubber and conventional vulcanizate thermoplastic elastomersare characterized as having a low gas permeability, resulting in slowtransmission of the sterilization gas into the passage in the needleshield containing the needle cannula. Further, because ethylene oxidegas is toxic, all of the sterilization gas must be removed from theneedle shield before packaging. Again, because of the slow transmissionof the sterilization gas out through the needle shield, the syringeassembly is quarantined until substantially all of the sterilization gaspermeates out through the shield. Unexpectedly, a styrene blockpoly(ethylene butylene) thermoplastic elastomer has a relatively highgas permeability to ethylene oxide gas as established by testing forresidual gas in the shield following sterilization.

The most preferred embodiment of the needle shield for a syringe needlecannula of this invention is formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer having a Shore hardnessof between 45 and 65. The most preferred composition for the needleshield of this invention also includes about one to three percentcolorant which contains carbon black to improve structural integrity andreduce coring.

Other advantages and meritorious features of the syringe assembly ofthis invention will be more fully understood from the followingdescription of the preferred embodiments, the appended claims, and thedrawings, a brief description of which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a syringe having the improved needle shield andneedle cannula point configuration of this invention;

FIG. 2 is a partially cross-sectioned view of FIG. 1;

FIG. 3 is an enlarged side cross-sectional view of the needle shieldshown in FIGS. 1 and 2;

FIG. 4 is a frontal perspective view of a multi-beveled needle tipgeometry in accordance with the present invention;

FIG. 5 is a top view of the multi-beveled needle tip of FIG. 4;

FIG. 6 is a side view of the multi-beveled needle tip of FIG. 4;

FIG. 7 is a front view of the multi-beveled needle tip of FIG. 4,depicting rotational angles about the central axis of the cannula forforming the multi-bevels and tip bevels;

FIG. 8 is a second view of a multi-beveled needle cannula tip inaccordance with the present invention, depicting the needle cannularotated about the central axis at a first rotational angle and inclinedat a planar angle with respect to an imaginary plane extending throughthe central axis for forming the middle bevels; and

FIG. 9 is a third view of the multi-beveled needle tip in accordancewith the present invention, depicting the needle cannula rotated at asecond rotational angle about the central axis of the needle cannula andinclined at a second planar angle with respect to an imaginary planeextending through the central axis for forming the tip bevels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The syringe assembly 20 illustrated in FIGS. 1 and 2 and the needleshield or sheath illustrated in FIGS. 2 and 3 may be generallyconventional in configuration except as described below and may takevarious forms within the purview of the appended claims. That is, thesyringe assembly 20 may be any conventional injection device, such asthe syringe assembly disclosed having a generally tubular barrel portion24 including a reduced diameter tip portion 26 and a needle cannula 30affixed by any suitable means to the tip portion 26 of the barrel, suchthat the lumen through the needle cannula is in fluid communication withthe interior 32 of the barrel. The barrel 24 is typically formed ofglass, but may also be formed of a suitable plastic, and the needlecannula 30 is typically formed of stainless steel. The sharp tip 34 ofthe needle cannula preferably includes a five-beveled point as shown inFIGS. 4-9 and described below.

The barrel 24 typically includes a radial flange 36 at its open endwhich receives a stopper assembly, including a plunger rod 38 and astopper 40 generally formed of an elastomeric material, such as naturalrubber or synthetic rubber. The resilient stopper 40 may be connected byany suitable means to the plunger rod 38, including a threadedconnection (not shown). As will be understood by those skilled in thisart, the resilient stopper 40 forms an interference sealed fit with theinterior surface 32 of the barrel such that as the plunger 40 isreciprocated through the barrel, a medicament, drug or vaccine may beaspirated from a vial, for example, or a medicament, drug or vaccine 44may be injected into a patient. However, the most preferred embodimentof this invention is a prefilled syringe for medical injections. Theplunger rod 38 may also include a radial flange 42 as shown to assistthe patient or healthcare worker during use of the syringe assembly 20.As set forth herein, the needle shield 22 of this invention isparticularly suitable for sterilization of prefillable or prefilledsyringe assemblies.

FIG. 3 is an enlarged cross-sectional view of the needle shield 22 shownin FIGS. 1 and 2. The needle shield includes an open end 46 which may beslightly tapered or conical as shown to receive the barrel tip portion26 of the barrel as shown in FIG. 2. The needle shield includes a closedend portion 48 and a needle passage 50 through the open end 46 with theneedle passage 50 having an inner wall 51 which seals against the tipportion 26 of the syringe. In this preferred embodiment, the needlepassage 50 includes an internal rib 52 which is received in a reduceddiameter portion of the tip portion 26 of the syringe barrel as shown inFIG. 2 to assure retention of the shield on the syringe. The needlepassage also includes a reduced diameter cylindrical portion 54 adjacentthe internal rib 52 which assists in retaining the needle shield on thetip portion of the syringe to avoid the needle shield popping off,especially during sterilization. The annular internal rib 52 maybecontinuous or interrupted to assist in removal from the mold. Thisembodiment also includes an external annular rib or flange 56, adjacentthe open end, which is adapted to receive and retain a rigid tubularshield which may be used to enclose the shield 22 as disclosed in theabove referenced U.S. Pat. No. 4,964,866.

As set forth above, the needle shield 22 of this invention is formed ofa styrene block thermoplastic elastomer, preferably a styrene blockpoly(ethylene/butylene) thermoplastic polymeric elastomer having a ShoreA hardness of between 30 and 90, most preferably between 45 and 65. Aneedle shield formed of this thermoplastic elastomer has severalimportant and unexpected advantages over conventional rubber shields andshields formed of conventional vulcanizate thermoplastic elastomers. Onevery important advantage of a syringe assembly having a needle shieldformed of a styrene block poly(ethylene/butylene) thermoplasticpolymeric elastomer is reduced needle penetration force as establishedby bench testing and clinical trials as follows. Three variables weretested by the applicant as part of a major program to reduce thepenetration force of syringe needles and improve patient comfort duringinjections. These variables included a comparison of (1) the five-bevelneedle point design disclosed herein and a standard three-bevel design,(2) needle lubricant (which is an aminofunctional polydimethylsiloxanecopolymer available from Dow Corning) and the conventional siliconelubricant, and (3) a needle shield formed of a styrene blockpoly(ethylene/butylene) thermoplastic polymeric elastomer having Shore Ahardness of between 45 and 65 and a conventional needle shield formed ofrubber. Previous bench testing showed no improvement in penetrationforce between sterilized syringes having a rubber needle shield and aneedle shield formed of a conventional vulcanizate thermoplasticelastomer, namely Santoprene® of Advanced Elastomer Systems of Akron,Ohio. Santoprene is a polypropylene ethylene-propylene terpolymerrubber-based vulcanizate. The needle shield formed of a styrene blockpoly(ethylene/butylene) thermoplastic polymeric elastomer was KRATON® G2705 available from Kraton Company of Houston, Tex. Other needle shieldsformed of other thermoplastic elastomers were also molded; however,various problems were encountered during molding, including shrinkage,cracking, etc. KRATON® polymers are available from Kraton Company inlinear, diblock, triblock and radial polymers. Each molecule of KRATON®polymers consists of block segments of styrene monomer units and rubbermonomer units. Each block's segment may consist of 100 monomer units ormore. The most common structures of the KRATON® polymers are the linearA-B-A block types: styrene-butadiene-styrene (SBS),styrene-isoprene-styrene (SIS). However, the KRATON® G series polymers,are specialized polymers of the radial (A-B)_(N) type and the mostpreferred thermoplastic elastomer for this application is KRATON® Gpolymer series, which is a polystyrene block poly(ethylene/butylene)thermoplastic elastomer. The KRATON® G 2705 polymer is also FDA approvedfor contact with foods. Of all of the variables tested, the mostsignificant improvement in penetration force verified by bench testingand reduced pain resulting from simulated injections verified byclinical testing, the most significant improvement was found with needleshields formed of a styrene block poly(ethylene/butylene) thermoplasticpolymeric elastomer, such as KRATON® G 2705, as discussed below.

The applicant conducted a full 16-week bench study comparing penetrationforces of syringes having needle shields formed of natural rubber andSantoprene® which, as stated above, is a polystyrene EPDM-basedvulcanizate thermoplastic elastomer available from Advanced ElastomerSystems. The study also included standard methods for accelerated agingfor five years. All of the syringes tested were sterilized by standardprocedures with ethylene oxide and part of the group of each syringetype in the evaluation were subsequently steam sterilized usingestablished parameters to simulate “terminal” sterilization. These benchtests determined that there was no difference within normal statisticalvariations between the penetration forces of syringes having needleshields formed of Santoprene® thermoplastic elastomers and naturalrubber. The natural rubber needle shields were formed of one of thecommon formulations of commercially available natural rubber used forneedle shields.

The applicant also conducted bench tests comparing penetration forces ofsyringes having needle shields formed of natural rubber and a styreneblock poly(ethylene/butylene) thermoplastic elastomer (KRATON® G 2705).This was a 16-week study with conventional syringes including needlecannulas having conventional 23 gauge needle cannulas with three bevelpoints and the needle cannulas were coated with conventional siliconelubricant. In surrogate tissue, the peak penetration force of syringeshaving needle shields formed of a styrene block poly(ethylene/butylene)thermoplastic elastomer (KRATON®G 2705) compared to natural rubberneedle shields following sterilization by ethylene oxide was reduced 16%following sterilization with ethylene oxide plus terminal steamsterilization. Bench testing in Faultless Vial Stoppers (FVST) of AbbottLaboratories, the force reduction was 5% in both cases, consistent withearlier results. Testing after eight weeks of aging showed similartrends and after 16 weeks of aging, the trend continued strongly. Insurrogate tissue, the peak force was reduced by 11% with needle shieldsformed of styrene block poly(ethylene/butylene) thermoplastic elastomercompared to natural rubber where the samples were sterilized withethylene oxide and 9.5% when the samples were sterilized with ethyleneoxide plus terminal steam sterilization. The following table summarizesthese results.

Peak Penetration Force Test Results, Grams (SD=Standard Deviation)

T = 8 wks. T = 8 wks. T = 16 wks. T = 16 wks. NS T = 0 T = 0 @60° C.@60° C. @60° C. @60° C. Material: EtO only EtO& T.S. EtO only EtO& T.S.EtO only EtO& T.S. Human skin substitute: Natural 204.50 220.49 197.25206.99 219.68 200.27 Rubber SC = 27.96 SD = 27.08 SD = 29.20 SD = 32.00SD = 52.22 SD = 29.95 Kraton 183.75 185.05 159.67 175.24 157.78 170.86G2705 SD = 34.49 SD = 25.41 SD = 15.37 SD = 17.95 SD = 28.89 SD = 24.77Faultless gray rubber vial stopper: Natural 471.24 464.97 521.97 530.74592.98 543.13 Rubber SD = 38.25 SD = 76.15 SD = 32.14 SD = 34.5 SD =121.3 SD = 42.10 Kraton 453.89 443.02 509.88 509.63 483.02 511.13 G2705SD = 28.28 SD = 33.65 SD = 37.26 SD = 31.43 SD = 27.71 SD = 51.57

Clinical tests were also conducted by the applicant with prefillablesyringe systems commercially available from the applicant. As set forthabove, these clinical trial were conducted to test three components ofsyringes, namely needle point configurations (3 vrs. 5 beveled needlepoints), needle lubricants and needle shields formed of natural rubberand styrene block (polyethylene/butylene) thermoplastic elastomer(KRATON® G 2705) to determine whether there was any significantdifference in either perceived pain or ease of penetration. The testswere conducted with 25 gauge, 16.7 mm. (⅝″) HYPAK® cannula needles. Theneedles were used for both subcutaneous (SC) and intramuscular (IM)injections. Although no significant difference was found in either painor ease of penetration between three and five-beveled needles withintramuscular injections, there was a significant improvement in ease ofpenetration scores (assessed by nurses) with subcutaneous injectionsusing the five-bevel needle design disclosed herein. Further, previousbench and clinical testing determined that 27 gauge needle cannulashaving the improved five-bevel design resulted in a 15% to 18% reductionin penetration force in human skin substitute as compared toconventional needle cannulas of the applicant having three bevels.

In the second clinical study conducted by the applicant, 12 nurses and14 subjects per nurse (168 subjects total) participated in a clinicaltrial to evaluate three factors with respect to pain, sharpness, and ageneral feeling of a particular injection. Only nurses who demonstratedsensitivity to differences in needle performance were chosen for thisstudy. Each subject received four subcutaneous injections in the arm,alternating between the arms. Subjects received only needle sticks, notactual injections from a syringe with no stopper or plunger. The threefactors studied (point configuration, lubrication and shield material)were crossed to create eight treatment combinations. The randomizationschedule accounted for blocking due to nurse, subject within nurse,order of injection and side injection. Sharpness, as perceived by thenurse, was measured on a visual analog scale (VAS), and ranges from zero(excellent sharpness) to 100 (dull) as perceived by the nurse wasrecorded. Each sharpness VAS entry was measured by two different people,with the average measurement being used for the data analysis. Thefeeling of the injection as perceived by the nurse was qualified withfive integer scale response variables. The overall feel of the injectionwas rated on a 13-point scale. The initial resistance, smoothness ofpenetration and roughness/shatters/ripping response variables weremeasured on a 4-point scale. In addition, each of the five responsiblevariables was oriented such that the lower scores were the preferredscores regarding product performance. Finally, the nurses made anoverall clinical acceptability assessment for each “injection”. “Initialresistance” was described as what was felt as the needle starts topuncture the skin and breaks through the epidermis layer (striatumcorneum). The data from these tests regarding initial resistanceestablished that a syringe having a needle cannula with a five-bevelconfiguration and a needle shield formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer had the least initialresistance and syringes having a three-beveled point with a needleshield formed of a styrene block poly(ethylene/butylene)thermoplastic-elastomer was second best. Syringes having needle shieldsformed of rubber received poor performance ratings.

“Smoothness in penetration” describes whether the patient or nurseperceived an increase in pressure at any point during the injectionprocess going in or during withdrawal. For going in, syringes having athree-beveled point with a styrene block poly(ethylene/butylene)thermoplastic elastomer was found clear-cut best. Syringes having afive-beveled point and a needle shield formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer were found second best.Again, the syringes having needle shields formed of rubber had thepoorest ratings. For withdrawal, no significant difference was foundbetween the type of needle cannula or lubricant, but needle shieldsformed of a styrene block poly(ethylene/butylene) thermoplasticelastomer were found preferable to syringes having rubber needleshields.

Finally, pain as perceived by the subject, was measured on a visualanalog scale (VAS) ranging from zero (no pain) to 100 (very severepain). Each pain VAS entry was measured by two different people, withthe average measurement being used for the data analysis. Pain was alsomeasured with the Gracely scale, an integer-valued scale that rangesfrom zero to 20. Although there was no statistically significantdifference in pain perception between the treatment groups, thetreatment groups where the injection was made with syringes having aneedle shield formed of a styrene block poly(ethylene/butylene)thermoplastic elastomer were perceived by the nurse as having a 50%improvement in sharpness and almost 30% less perceived pain by thepatient compared to conventional syringes having a rubber needle shield.

On the basis of this clinical study, the applicant determined that theprimary improvement in perceived sharpness and reduced pain resultedfrom the substitution of a needle shield formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer (KRATON® G 2705) for anatural rubber shield. No significant difference in these tests werefound with changes of the needle lubricant. Needle shield removaltesting also established that a needle shield formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer with about one to threepercent by weight colorant including carbon black maintained a range ofremoval forces from the syringe barrel tip that were acceptable ascompared to the control. There were no separation failures of thesamples with styrene block poly(ethylene/butylene) thermoplasticelastomers.

The addition of up to about two percent by weight of colorant includingcarbon black was found to reduce needle coring by about 80%. Colorantincluding Carbon black was added to the styrene block thermoplasticelastomer (KRATON® G 2705) in a ratio of 50 to one or 2% colorant. Thecolorant included about ⅔ styrene based resin carrier, such that thecarbon black content was about ⅓ of the content of the colorant or about0.66% of the thermoplastic elastomer. The carbon black colorant used wasUN0055P from Clariant Company at Holden, Mass. Tests conducted of needleshields having about four percent of colorant including carbon black didnot reduce coring as well. Thus, the most preferred composition of theneedle shield includes about one to three percent carbon black colorant.

The improved results with needle shields formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer is not fully understood.It is believed, however, that rubber shields either wipe away or absorbthe needle lubricant, resulting in greater perceived pain. This beliefwas confirmed by microscopic examination of the needle point, whereinneedle lubricant was observed on needle points which were enclosed witha needle shield formed of a styrene block poly(ethylene/butylene)thermoplastic elastomer (KRATON® G 2705) and no lubricant was observedon needle points which were enclosed by rubber needle shields. Anotherpossibility is that the filler used in conventional rubber formulationsis abrasive, resulting in abrasion of the needle point and increasedpain. Thus, while the needle point configuration and lubricant were notdeemed to be statistically significant in such clinical trial, thesignificance of the needle point configuration may have been masked inthese tests.

The applicants believe that another advantage of syringes having needleshields formed of a styrene block poly(ethylene/butylene) thermoplasticelastomer will be improved gas permeability over rubber needle shieldsand shields formed of vulcanizate thermoplastic elastomers such asSantoprene®. As set forth above, hypodermic syringe assemblies includingprefilled syringes must be sterilized before use. Typically, hypodermicsyringes are sterilized by immersion in ethylene oxide or steam asdescribed above. However, because ethylene oxide gas is toxic, the gasmust be removed prior to packaging. Rubber and other vulcanizatethermoplastic elastomers, such as Santoprene®, are reported to have alow gas permeability. Although no ethylene oxide gas permeabilitycomparisons are readily available for ethylene oxide gas, the applicantcompared ethylene oxide gas residuals between needle shields formed of astyrene block poly(ethylene/butylene) thermoplastic elastomer having upto one percent carbon black (KRATON® G 2705). and a blend of naturalrubber and styrene butadiene rubber. These tests were conducted byimmersion of the syringe assemblies in purified water aftersterilization with ethylene oxide gas with a needle shield with andwithout a rigid needle shield guard as disclosed in the above referencedU.S. Patent. The following table summaries the test results, wherein theethylene oxide (EtO) gas residuals for the simulation of use for theKRATON® G 2705 needle shields were below the limit of 0.4 μg/ml and theethylene chlorydrine residuals were below the limit of 12.5 μg/ml. Thus,the results were better for needle shields formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer than a rubber blend ofnatural and synthetic shields.

1 EtO Cycle 2 EtO Cycles Rubber Blend RNS TPE Rubber Blend RNS TPE Testby No detection No detection 3.5 μg/ml 0.1 μg/ml simulation of use Testby 1.8 μg/g 0.3 μg/g 3.0 μg/g 2.0 μg/g immersion without the plasticrigid shield Test by 1.9 μg/g 1.3 μg/g 2.7 μg/g 1.7 μg/g immersion withthe plastic rigid shield

Based upon this test, the applicant believes that the improved gaspermeability of needle shields formed of styrene blockpoly(ethylene/butylene) thermoplastic elastomers will reduce gassterilization cycle time over rubber needle shields and shields formedof vulcanizate thermoplastic elastomers including Santoprene® and reduceethylene oxide gas residuals following sterilization.

In the following description of FIGS. 4 to 9, the term “proximal”denotes a direction closest to a practitioner, while the term “distal”denotes a direction furthest from a practitioner. FIGS. 4 to 9 depict ahypodermic needle 110 characterized by a multi-beveled point 120 inaccordance with the present invention. As the skilled artisan willappreciate, hypodermic needle 110 can be formed from a tube or cannula111 defining therein a fluid carrying duct or lumen 116. Hypodermicneedle 110 includes a proximal end 114 which can be attached in fluidcommunication with a medical delivery instrument, such as the syringeshown in FIGS. 1 and 2. Multi-beveled point 120 defines a fluid opening122 for passage of fluids to and from fluid carrying lumen 116. Thefluid carrying lumen is characterized by a central axis 118.

Multi-beveled point 120 is characterized by a length “L” and is formedthrough a plurality of individual bevels that together define a beveledface 140 about the periphery of fluid opening 122. In the embodimentdisclosed by applicants herein, the multi-beveled point is characterizedby a primary bevel 130; a pair of middle bevels 132 a, 132 b; and a pairof tip bevels 134 a, 134 b. Each of the pair of middle bevels 132 a, 132b and each of the pair of tip bevels 134a, 134 b are substantiallysymmetrically formed on opposite sides of primary bevel 130, as will befurther described hereinbelow. Adjacent middle and tip bevels 132 a, 134a meet at an intersect 138 a demarcating the respective planes at whichthe middle and tip bevels are formed. Adjacent middle and tip bevels 132b, 134 b likewise meet at an intersect 138 b. Tip bevels 134 a, 134 bmeet at appointed apex 136 which first enters the skin of a patient (orsealing material associated with a fluid carrying vessel). As shown inthe FIGS., certain bevels may be formed with greater lengths than otherbevels. For example, with reference to FIG. 5, and considering themiddle bevel 132 a as a first bevel, and counting clockwise therefrom(i.e., the primary bevel 130 is a second bevel; the middle bevel 132 bis a third bevel; the tip bevel 134 b is a fourth bevel; and the tipbevel 134 a is a fifth bevel), the first and third bevels (e.g., themiddle bevels 132 a and 132 b) may be formed with lengths greater thanthe second, fourth and fifth bevels (e.g., the primary bevel 130 and thetip bevels 134 a and 134 b).

It has been surmised by the applicants herein and confirmed by the benchpenetration tests discussed above that optimum results for reducing theheight of intercepts 138 a, 138 b is achieved by forming primary bevel130 and each of middle bevels 132 a, 132 b at angles of inclination 130Ωand 132Ω which are substantially equal if not identical. For instance,it has been found by applicants herein that optimum results are achievedby setting both inclination angles 130Ω and 132Ω, respective toimaginary plane 150, in a range of about 9 degrees (“°”) plus or minus1°. For purposes of simplicity, the transition demarcating primary bevel130 from each of middle bevels 132 a, 132 b has been denoted by thenumeral 131. It is surmised that by not varying the angle of inclination132Ω for the middle bevels from angle of inclination 130Ω for theprimary bevel, transition 131 demarcating primary bevel 130 from middlebevels 132 a, 132 b will be more rounded and less pronounced,contributing to a smoother, more continuous bevel face 140. Subsequentto formation of primary bevel 130, the hypodermic needle is rotatedabout the central axis 118 in both the clockwise and counterclockwisedirections at rotational angle 132λ to form middle bevels 132 a, 132 b.It has been found by the applicants herein that optimum results areobtained when the range of rotational angle 132λ is about 8.5° plus orminus 5°.

Tip bevels 134 a, 134 b are likewise formed or otherwise provided onhypodermic needle 110 by inclining central axis 118 of hypodermic needle110 to an angle 134Ω relative to reference plane 150, and by rotatingthe hypodermic needle about central axis 118 to an angle 134λ. It hasbeen found by the applicants herein that optimum results for reducingthe height of intercepts 138 a, 138 b demarcating the respective middleand tip bevels results when needle cannula 110 is inclined at an angle134Ω in a range of about 15° plus or minus 2°, and when the needlecannula is rotated to an angle 134λ in a range measuring about 23° plusor minus 5°.

FIG. 6 exemplifies the side profile of multi-beveled needle tip 120formed in accordance with the present invention. Intercept 138 a isreduced in height to an extent that when viewed from the side, middlebevel 132 a and tip bevel 134 a appear to provide asubstantially-straight profile. The same effect can be seen in FIG. 9,where middle and tip bevels 132 b, 134 b, when viewed in side profile,define an angle “π” that is nearly 180° as measured about intercept 138b. The effect is a more continuous bevel face 140 free of abruptintercepts 138 a, 138 b (or for that matter, transitions 131 demarcatingthe primary middle bevels), resulting in a needle tip requiring lesspenetration force. By reducing the heights of intercepts 138 a, 138 b,the effective outer diameter of needle point 120 is reduced, helping toreduce needle penetration forces.

The hypodermic needle 110 in accordance with the present invention canbe formed from conventional materials such as steel or more preferablystainless steel. It will be realized by the skilled artisan that medicalgrade plastics, composites, ceramics, or like materials can besubstituted. The needle is preferably lubricated with variousconventional lubricants such as silicone oils to enhance the effectsobtained by applicant's geometry. The bevels can be formed on thehypodermic needle by conventional processes such as by grinding.

It will be evident to the skilled artisan that the bevels can be formedin any order desired. In one iteration, the primary and middle bevelscan be formed before the tip bevels, in that in the preferredembodiment, the primary and middle bevels are formed at substantiallyidentical angles of inclination 130Ω, 132Ω, and this might contribute togreater manufacturing efficiency. However, other manufacturingiterations can be employed. For instance, the tip bevels can be formedprior to manufacturing either of the middle or primary bevels. A furtheriteration would be to form the middle bevels 132 a, 132 b intermediatethe steps required for forming primary bevel 130 and tip bevels 134 a,134 b. For instance, the central axis of the hypodermic needle can befirst inclined to angle 130Ω for formation of the primary bevel.Thereafter, the central axis of the hypodermic needle can be inclined toangle 134Ω, and thereafter rotated about central axis 118 to angles ofrotation 134λ, for formation of the tip bevels. Thereafter, central axisof hypodermic needle 110 can be re-inclined to angle 132Ω, and rotatedabout central axis 118 to angles 132λ, for formation of the middlebevels. It will be realized by the skilled artisan that any order forforming the respective bevels for needle tip 120 that results incontinuous bevel face 140 will achieve the advantages and results of theinvention herein.

Tests were conducted comparing penetration force in rubber vial stoppers(20 millimeter rubber vial stoppers, model number 88-29530, manufacturedby Abbott Laboratories of Ashland, Ohio) of 26 gauge needles produced inaccordance with the above-identified steps against penetration forcesexhibited by existing 26 gauge needles currently employed inHYPAK®-brand prefillable syringes, manufactured by Becton DickinsonPharmaceutical Systems of Le Pont de Claix, France. Each of the needleswere lubed with polydimethylsiloxane. Various angles of rotation 132λ,134λ and angles of inclination 130Ω, 132Ω and 134Ω were tested. Theresulting table illustrates that 26 gauge needles displaying needlepoint 120 according to the invention had significantly reduced needlepenetration forces as compared to existing product:

26G 5-Bevel Needles All needles lubed with polydimethylsiloxane RubberVial Penetration Forces in Gram Force (Average HYPAK Brand NeedleControl Force = 468.5 gmf) Angle of Angle Of Rotation Inclination 132 λ134 λ 130 Ω, 134 Ω Point Length Point Length 132 Ω (“L”) .094 .080″ TipBevel Tip Bevel Length Length .036″ .040″ 35° 35° 10° 10° 341.5 gm · f30° 30° 10° 10° 338.1 gm · f 22° 22° 10° 16° 344.5 gm · f 22° 22° 13°16° 359.0 gm · f

The formation of a multi-beveled tip as described herein results in abevel face 140 which is more continuous, free of abrupt intercepts ortransitions. Absent abrupt intercepts or transitions, the likelihoodthat a portion of the, bevel face will catch the skin or flesh or apatient is reduced, and the effective outside diameter of the needlepoint will be reduced, all meaning that needle penetration forces willbe lessened.

Having described preferred embodiments of the syringe assembly includingthe improved needle shield and multi-beveled needle point, it will beunderstood by those skilled in this art that various modifications maybe made within the purview of the appended claims. As described above,the method of making a sterilized syringe assembly of this invention,wherein the needle shield is formed of a styrene block thermoplasticelastomer, particularly a styrene block poly(ethylene/butylene)thermoplastic elastomer, has particular advantages for prefillable andprefilled syringes including improved needle sharpness, reducedperceived pain and it is believed that the improved needle shield willalso reduce gas sterilization cycle time. The improved five-bevel needleconfiguration described herein may be utilized in combination with theimproved needle shield to obtain superior results particularly withsmaller needle gauges, such as 27 gauge needle cannulas or smaller. Forexample, in an alternative embodiment, the subject invention can be usedwith a thin-walled 29 gauge needle having an outer diameter of astandard 29 gauge needle in the range of 0.130″-0.0135″. With itsthin-walled structure, the needle has. an inner diameter in the range of0.0075″-0.0090″ and preferably, the needle is provided with a wallthickness in the range of 0.00225″-0.00275″, although the toleranceranges for the inner and outer diameters allows for a wall thickness inthe range of 0.002″-0.003″. A standard 29 gauge needle has a nominalinner diameter of 0.007″ plus 0.001″/minus 0.005″ with a preferrednominal wall thickness of 0.003±0.00025″. Preferably, with a thin-walled29 gauge needle, the following angles are provided to form afive-beveled point as disclosed above: angles 130Ω and 132Ω are in therange of 8.5°±2.0°; angle 134Ω is 21°±2.0°; and angles 132λ and 134λ are22°±10°. Clearly, the thin-walled 29 gauge needle may be used withoutthe disclosed needle shield also.

The syringe assembly of this invention may take additional formsparticularly in regard. to the injection device including theconfiguration of the barrel, the attachment of the needle cannula to thebarrel and the plunger and stopper assembly, an embodiment of which isdisclosed herein for illustration purposes only. Further, theconfiguration of the needle shield shown in FIGS. 1 to 3, may bemodified as required for the application and preferably. includes arigid needle shield guard.

1. A syringe as assembly comprising: a syringe barrel; and, a needlecannula supported by said syringe barrel, said needle cannula having alumen and a central axis, an outer diameter in the range of0.0130″-0.0135″, and an inner diameter in the range of 0.0075″-0.0090″,said needle cannula having a multi-beveled point including a pluralityof planar bevels extending at different angles relative to said centralaxis, including a primary bevel, a pair of tip bevels and a pair ofmiddle bevels intermediate said primary bevel and said tip bevels, saidbevels contiguously bounding said lumen, wherein each of said bevels isgenerally flat.
 2. A syringe assembly as in claim 1, wherein, respectiveof angles defined between said central axis and a reference planes saidprimary bevel is provided at a first planar angle, said pair of middlebevels are provided at a second planar angle, and said pair of tipbevels are provided at a third planar angle, and wherein respective ofan angle of rotation about said central axis, said primary bevel isprovided at a first rotational angle, said pair of middle bevels areeach provided at a second rotational angle, and said pair of tip bevelsare each provided at a third rotational angle.
 3. A syringe assembly asin claim 2, wherein said first and second planar angles aresubstantially equal.
 4. A syringe assembly as in claim 2, wherein saidfirst and second planar angles are in the range of 8.5°±2.0°.
 5. Asyringe assembly as in claim 2, wherein said third planar angle is inthe range of 21 °±2.0°.
 6. A syringe assembly as in claim 2, whereinsaid second and third rotational angles are substantially equal.
 7. Asyringe assembly as in claim 6, wherein said second and third rotationalangles are in the range of 22°±10°.
 8. A syringe assembly as in claim 1,wherein said needle cannula defines a wall thickness between said innerand outer diameters in the range of 0.00225″-0.00275″.
 9. A syringeassembly as in claim 1 further comprising a needle shield having an openend and a passage through said open end configured to receive saidneedle cannula and said needle cannula disposed therein, wherein saidneedle shield is formed of a styrene block thermoplastic elastomerhaving a Shore A hardness of between 30 and
 90. 10. A syringe assemblyas in claim 9, wherein said needle shield is formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer.
 11. A syringe assemblycomprising: a syringe barrel; and, a needle cannula supported by saidsyringe barrel and having a multi-beveled point, said needle cannulahaving a central-axis, an outer diameter in the range of0.0130″-0.0135″, and an inner diameter in the range of 0.0075″-0.0090″,said needle cannula having a lumen and a central axis therethrough, saidmulti-beveled point provided at one end of the cannula, saidmulti-beveled point comprised of a primary bevel, a pair of tip bevels,and a pair of middle bevels, said bevels contiguously bounding saidlumen, wherein respective of an angle defined between said central axisand a reference plane coinciding with a respective said bevel, each ofsaid primary bevel, said pair of middle bevels, and said pair of tipbevels are provided on said cannula at a respective planar angle,wherein said planar angles of said primary bevel and said pair of middlebevels are substantially equal.
 12. A syringe assembly as in claim 11,wherein, respective of angles defined between said central axis and areference plane, said primary bevel is provided at a first planar angle,said pair of middle bevels are provided at a second planar angle, andsaid pair of tip bevels are provided at a third planar angle, andwherein respective of an angle of rotation about said central axis, saidprimary bevel is provided at a first rotational angle, said pair ofmiddle bevels are each provided at a second rotational angle, and saidpair of tip bevels are each provided at a third rotational angle.
 13. Asyringe assembly as in claim 12, wherein said second and thirdrotational angles are substantially equal.
 14. A syringe assembly as inclaim 13, wherein said second and third rotational angles are in therange of 22°±10°.
 15. A syringe assembly as in claim 11, wherein saidplanar angles of said primary bevel and said pair of middle bevels aresubstantially in the range of 8.5°±2.0°.
 16. A syringe assembly as inclaim 11, wherein said planar angle of said pair of tip bevels is in therange of 21°±2.0°.
 17. A syringe assembly as in claim 11, wherein saidneedle cannula defines a wall thickness between said inner and outerdiameters in the range of 0.00225″-0.00275″.
 18. A syringe assembly asin claim 11, further comprising a needle shield having an open end and apassage through said open end configured to receive said needle cannulaand said needle cannula disposed therein, wherein said needle shield isformed of a styrene block thermoplastic elastomer having a Shore Ahardness of between 30 and
 90. 19. A syringe assembly as in claim 18,wherein said needle shield is formed of a styrene blockpoly(ethylene/butylene) thermoplastic elastomer.
 20. A syringe assemblycomprising: a syringe barrel; and, a needle cannula supported by saidsyringe barrel and having a multi-beveled point, said needle cannulahaving a central axis, an outer diameter in the range of0.0130″-0.0135″, and an inner diameter in the range of 0.0075″-0.0090″,said multi-beveled point comprised of five bevels, wherein each of saidfive bevels is provided on said cannula at a planar angle definedbetween said central axis and a reference plane, and wherein each ofsaid five bevels is provided on said cannula at an angle of rotationabout said central axis, a reference axis being disposed perpendicularlyto said axis, wherein a first planar angle is defined at said bevelcorresponding to a first rotational angle, said first rotational anglebeing measured from said reference axis, a second planar angle isdefined at said bevel corresponding to a second rotational angle, saidsecond rotational angle being measured from said reference axis, saidfirst and second rotational angles being different with said first andsecond planar angle being substantially equal.
 21. A syringe assembly asin claim 20, wherein said two of said planar angles are substantially inthe range of 8.5°±2.0°.
 22. A syringe assembly as in claim 20, whereinat least one of said planar angles is in the range of 21°±2.0°.
 23. Asyringe assembly as in claim 20, wherein at least two of said rotationalangles are substantially equal.
 24. A syringe assembly as in claim 20,wherein at least two of said rotational angles are in the range of22°±10°.
 25. A syringe assembly as in claim 20, wherein said needlecannula defines a wall thickness between said inner and outer diametersin the range of 0.00225″-0.00275″.
 26. A syringe assembly as in claim20, further comprising a needle shield having an open end and a passagethrough said open end configured to receive said needle cannula and saidneedle cannula disposed therein, wherein said needle shield is formed ofa styrene block thermoplastic elastomer having a Shore A hardness ofbetween 30 and
 90. 27. A syringe assembly as in claim 26, wherein saidneedle shield is formed of a styrene block poly(ethylene/butylene)thermoplastic elastomer.
 28. A syringe assembly comprising: a syringebarrel; and, a needle cannula supported by said syringe barrel andhaving a multi-beveled point, said needle cannula having a central axis,an outer diameter in the range of 0.0130″-0.0135″, and an inner diameterin the range of 0.0075″-0.0090″, said needle cannula having a lumenextending from a first end of said cannula and having an opening definedthrough said first end, said multi-beveled point comprised of a pointwith first, second, third, fourth and fifth bevels contiguously boundingsaid opening, said first bevel contiguously extending between said fifthand second bevels, said second bevel contiguously extending between saidfirst and third bevels, said third bevel contiguously extending betweensaid second and fourth bevels, said fourth bevel contiguously extendingbetween said third and fifth bevels, and said fifth bevel contiguouslyextending between said fourth and first bevels, wherein said first andthird bevels each have a greater length than each of said second bevel,said fourth bevel, and said fifth bevel.
 29. A syringe assembly as inclaim 28, wherein said second bevel is provided on said cannula at afirst planar angle, said first and third bevels are provided on saidcannula at a second planar angle, and said fourth and fifth bevels areprovided on said cannula at a third planar angle.
 30. A syringe assemblyas in claim 29, wherein said first and second planar angles aresubstantially equal.
 31. A syringe assembly as in claim 29, wherein saidfirst and second planar angles are substantially in the range of8.5°±2.0°.
 32. A syringe assembly as in claim 29, wherein said thirdplanar angle is in the range of 21°±2.0°.
 33. A syringe assembly as inclaim 28, wherein said first, second, third, fourth and fifth bevelscomprise a primary bevel, a pair of tip bevels, and a pair of middlebevels, each of said pair of middle bevels being intermediate saidprimary bevel and one of said pair of tip bevels.
 34. A syringe assemblyas in claim 33, wherein, respective of angles defined between saidcentral axis and a reference plane, said primary bevel is provided at afirst planar angle, said pair of middle bevels are provided at a secondplanar angle, and said pair of tip bevels are provided at a third planarangle, and wherein respective of an angle of rotation about said centralaxis, said primary bevel is provided at a first rotational angle, saidpair of middle bevels are each provided at a second rotational angle,and said pair of tip bevels are each provided at a third rotationalangle.
 35. A syringe assembly as in claim 34, wherein said second andthird rotational angles are substantially equal.
 36. A syringe assemblyas in claim 35, wherein said second and third rotational angles are inthe range of 22°±10°.
 37. A syringe assembly as in claim 28, whereinsaid needle cannula defines a wall thickness between said inner andouter diameters in the range of 0.00225″-0. 00275″.
 38. A syringeassembly as in claim 28, further comprising a needle shield having anopen end and a passage through said open end configured to receive saidneedle cannula and said needle cannula disposed therein, wherein saidneedle shield is formed of a styrene block thermoplastic elastomerhaving a Shore A hardness of between 30 and
 90. 39. A syringe assemblyas in claim 38, wherein said needle shield is formed of a styrene blockpoly(ethylenelbutylene) thermoplastic elastomer.
 40. A syringe assemblycomprising: a syringe barrel; and, a needle cannula supported by saidsyringe barrel and having a multi-beveled point, said needle cannulahaving a central axis, an outer diameter in the range of0.0130″-0.0135″, and an inner diameter in the range of 0.0075″-0.0090″,said cannula having a lumen, said lumen extending from a first end ofsaid cannula and having an opening defined through said first end, saidfirst end terminating in a point with a plurality of discrete bevelscontiguously bounding said opening, wherein one of said plurality ofdiscrete bevels is located furthest from said point and has a lengthshorter than any of said other ones of said plurality of discretebevels.
 41. A syringe as in claim 40, wherein said plurality of discretebevels comprise a primary bevel, a pair of tip bevels, and a pair ofmiddle bevels, each of said pair of middle bevels being intermediatesaid primary bevel and one of said pair of tip bevels, whereinrespective of an angle defined between said central axis and a referenceplane, each of said primary bevel, said pair of middle bevels, and saidpair of tip bevels are provided on said cannula at a respective planarangle, wherein said planar angles of said primary bevel and said pair ofmiddle bevels are substantially equal.
 42. A syringe assembly as inclaim 41, wherein, respective of angles defined between said centralaxis and a reference plane, said primary bevel is provided at a firstplanar angle, said pair of middle bevels are provided at a second planarangle, and said pair of tip bevels are provided at a third planar angle,and wherein respective of an angle of rotation about said central axis,said primary bevel is provided at a first rotational angle, said pair ofmiddle bevels are each provided at a second rotational angle, and saidpair of tip bevels are each provided at a third rotational angle.
 43. Asyringe assembly as in claim 42, wherein said second and thirdrotational angles are substantially equal.
 44. A syringe assembly as inclaim 43, wherein said second and third rotational angles are in therange of 22°±10°.
 45. A syringe assembly as in claim 41, wherein saidplanar angles of said primary bevel and said pair of middle bevels aresubstantially in the range of 8.5°±2.0°.
 46. A syringe assembly as inclaim 41, wherein said planar angle of said pair of tip bevels is in therange of 21°±2.0°.
 47. A syringe assembly as in claim 40, wherein saidneedle cannula defines a wall thickness between said inner and outerdiameters in the range of 0.00225″-0.00275″.
 48. A syringe assembly asin claim 40, further comprising a needle shield having an open end and apassage through said open end configured to receive said needle cannulaand said needle cannula disposed therein, wherein said shield is formedof a styrene block thermoplastic elastomer having a Shore A hardness ofbetween 30 and
 90. 49. A syringe assembly as in claim 48, wherein saidneedle shield is formed of a styrene block poly(ethylene/butylene)thermoplastic elastomer.